JP4889928B2 - Reference coordinate calculation method, reference coordinate calculation program, recording medium, surface plate, and shape measuring apparatus - Google Patents

Description

  The present invention relates to a reference coordinate calculation method, a reference coordinate calculation program, a recording medium thereof, a surface plate, and a shape measuring apparatus. For example, the present invention relates to a reference coordinate calculation method for obtaining the positions (coordinates) of each reference point provided over a wide range as coordinate points on a single reference coordinate.

Conventionally, the shape of an object to be measured is measured with a three-dimensional measuring machine or the like. However, since the measurement area is limited to the stage of the coordinate measuring machine, the size of the object to be measured is limited.
Therefore, in order to enlarge the measurement region, for example, a method disclosed in Patent Document 1 is known.
In this method, a movable measuring machine and a plurality of reference point groups whose coordinate values are obtained in advance are prepared. Then, the shape of the object to be measured is measured with the movable measuring machine while moving the movable measuring machine in accordance with the part to be measured of the object to be measured. In addition, the position of the movable measuring machine is obtained based on the result of measuring each reference point. By synthesizing the measurement data obtained by measuring the object to be measured with the measuring machine according to the position of the measuring machine each time, the entire shape of the object to be measured is obtained.

Japanese Patent Laid-Open No. 11-6728

  However, when setting a reference point group for determining the position of a movable measuring machine, the coordinates of each reference point are measured and registered by a measuring machine (such as a three-dimensional measuring machine) that includes all the reference points in the measurement area. Was. Therefore, there is a problem that a very large measuring machine is required. It is not easy to prepare such a large measuring machine, and there is a problem that, for example, a large place and a large cost are required to install as a general factory facility.

  An object of the present invention is to provide a reference coordinate calculation method, a reference coordinate calculation program, and a recording medium for determining the coordinates of a reference point in a wider range than the measurement area of the measuring machine, and also to have a wider area than the measurement area of the measuring machine. An object of the present invention is to provide a surface plate and a shape measuring device for measuring a workpiece in a range.

The reference coordinate calculation method of the present invention is a reference coordinate calculation method for obtaining the positions of a plurality of reference points arranged on a surface plate wider than the measurement area of the measuring machine as coordinate points on a single reference coordinate system, The reference points included in a region that can be measured without moving the position of the measuring machine itself as one group, and each group obtained by grouping a plurality of the reference points is at least one other group. A grouping step that includes three reference points in common and all groups form a closed loop having no start point group and no end point group as a whole, and are grouped so as to be connected in series, and the reference for each group The measurement process of measuring the position of the point with the measuring instrument, and the respective positions obtained by measuring in different groups with respect to a reference point common to different groups A reference point coordinate conversion function calculation step for calculating a reference point coordinate conversion function for converting the coordinate points to the same or extremely approximate coordinate points for each group, and a position of each reference point measured for each group is calculated for each group. And a reference point coordinate conversion processing step of converting the coordinates by the reference point coordinate conversion function.

According to this configuration, the reference points arranged in a wide area can be grouped, and the position of the reference point measured for each group can be converted into a coordinate point on the reference coordinate system using the coordinate conversion function for each group. . Therefore, the coordinates of the reference point can be calculated as points on the reference coordinate system in a wide area regardless of the measurement area of the measuring machine. Therefore, it is not necessary to prepare a large measuring machine that includes all of the reference points in the measurement region, so that excellent cost reduction can be achieved. In addition, since there is no restriction on the size of the area where the reference points are arranged, it is possible to provide reference points in areas as wide as necessary and obtain the positions of these reference points as coordinate points on the reference coordinate system. .
In the grouping process, the user may group the reference points so as to satisfy the requirements described in the claims while considering the relationship between the reference point arrangement and the measurement area of the measuring machine, or the reference point arrangement. You may make it carry out by the part program which groups automatically according to the relationship between a state and the measurement area | region of a measuring machine.

The reference coordinate calculation method of the present invention is a reference coordinate calculation method for obtaining the positions of a plurality of reference points arranged on a surface plate wider than the measurement area of the measuring machine as coordinate points on a single reference coordinate system, The reference points included in a region that can be measured without moving the position of the measuring machine itself as one group, and each group obtained by grouping a plurality of the reference points is at least one other group. A grouping step that includes two reference points and a common plane in common, and that all groups form a closed loop that does not have a start point group and an end point group as a whole, and are grouped so as to be connected in series. A measuring step of measuring the position of the reference point and the common plane with the measuring instrument every time, and the reference point and the common plane common to different groups A reference point coordinate conversion function calculation step for calculating, for each group, a reference point coordinate conversion function for converting each position obtained by measurement in a different group to a coordinate point that is the same or extremely approximate, and for each group A reference point coordinate conversion processing step of performing coordinate conversion of the measured position of each reference point by the reference point coordinate conversion function calculated for each group.

  In the present invention, it is preferable that the position of the reference point is a position projected on the common plane.

According to such a configuration, the same effects as those of the above-described invention can be achieved.
That is, regardless of the measurement area of the measuring machine, the reference point coordinates of a plurality of reference points arranged on a wide surface plate can be obtained as points on the reference coordinate system.
Here, as a general rule, when measuring a common reference point between groups and combining the measurement results for each group based on the coordinates of these common reference points as a point on a unified coordinate system, an n-dimensional coordinate system Thus, n common reference points are required between the groups. In this respect, in the present invention, the coordinate point where the position of the reference point is projected on the common plane is obtained as the reference point coordinates, and there are two or more reference points common between the groups, and the common plane in each group By measuring the above, it is possible to obtain substantially the same effect as including three reference points in common among the groups, and even if there are two reference points common to the groups, The coordinates of the measured reference point can be combined with the unified coordinates. In this way, since two reference points can be shared between groups, the grouping conditions are relaxed compared to the case where three groups are shared, and grouping can be performed easily.

  Note that the position of the reference point does not necessarily have to be the coordinates projected on the common plane, and the coordinate conversion is performed by obtaining a reference point coordinate conversion function for each group based on the positions of the two reference points and the common plane. It is good.

An example of the common plane is a surface plate of a surface plate. Further, examples include cases where the center of a true sphere fitted in a hole drilled in the surface plate surface is used as a reference point, or the apex of a conical hole drilled in the surface plate surface is used as a reference point. . Then, the reference point thus provided may be used as the reference point coordinates for each reference point by projecting the reference point on the surface plate.
When the center of the true sphere is used as the reference point, the center coordinates of the sphere may be calculated by measuring four points on the surface of the sphere. The common plane can be obtained by measuring any three points on the surface plate surface that are not positioned on a straight line.

The reference point coordinate calculation method of the present invention is a coordinate point on a single reference coordinate system in which the positions of a plurality of reference points, which are points on a two-dimensional coordinate system arranged on a surface plate wider than the measurement area of the measuring machine. The reference coordinate calculation method is obtained as follows: at least one group obtained by grouping a plurality of the reference points with the reference points included in an area that can be measured without moving the position of the measuring machine itself as one group. Group including at least two of the reference points in common with two other groups, and all groups form a closed loop having no start point group and no end point group as a whole, and are connected in a series. A grouping step, a measurement step of measuring the position of the reference point for each group by the measuring instrument, and a common reference point between different groups. A reference point coordinate conversion function calculation step for calculating a reference point coordinate conversion function for each group, the coordinate conversion function for converting the position of each of the obtained positions to the same or very close coordinate point, and each of the measured points for each group A reference point coordinate conversion processing step of converting the position of the reference point by the reference point coordinate conversion function calculated for each group.

According to such a method, the same effect as the above-mentioned invention can be produced. That is, regardless of the measurement area of the measuring machine, the position of the reference point arranged on a wide surface plate can be calculated as a point on the reference coordinate system.
Since the reference point is a point on the two-dimensional coordinate system, two reference points may be common to the groups.
An example of a measuring machine that uses such a two-dimensional coordinate system reference point is an image measuring device.

In the present invention, in the reference point coordinate conversion function calculation step, each coordinate point obtained by performing coordinate conversion using the coordinate conversion function on a position obtained by measuring the same reference point with a different group is calculated based on the average value. It is preferable to calculate the reference point coordinate conversion function that obtains the deviation having and minimizes the sum of squares of the deviation.
According to this configuration, the reference point coordinate conversion function for each group can be obtained by the method of least squares.

  The reference coordinate calculation program of the present invention causes a computer to execute each step of the reference point coordinate calculation method. That is, the computer is caused to execute a grouping step, a reference point coordinate conversion function calculating step, and a reference point coordinate conversion processing step.

  The recording medium of the present invention is characterized in that the reference coordinate calculation program is recorded so as to be readable by a computer.

According to such a configuration, the same effects as those of the above-described invention can be achieved. That is, the coordinates of the reference point can be calculated as points on the reference coordinate system in a wide area regardless of the measurement area of the measuring machine. Therefore, it is not necessary to prepare a large measuring machine that includes all of the reference points in the measurement area, and the reference points are provided in a wide area as necessary, and the positions of the reference points are set on the reference coordinate system. It can be obtained as a coordinate point.
If a program is configured to cause a computer having a CPU (central processing unit) and a memory (storage device) to execute each of the above steps, the parameters in each step can be easily changed.
For example, in the grouping step, it is easy to change the number of reference points that are common among the groups, or to input and change the reference point arrangement interval, the measurement area of the measuring machine, and the like. Alternatively, in the reference point coordinate conversion function calculation step, it is easy to change the calculation method for calculating the reference point coordinate conversion function for each group to various calculation methods in addition to the least square method.
The program may be installed by directly or indirectly loading the recording medium on which the program is recorded into the computer, and a reading device that reads information on the recording medium is externally attached to the computer, and the program is loaded from the reading device to the computer. May be installed. The program may be supplied and installed on the computer via a communication line such as the Internet, a LAN cable, a telephone line, or wirelessly.
Any language can be used to describe the program, regardless of whether it is an assembler, compiler, text format, or graphical format. It doesn't matter.

The surface plate of the present invention has a plurality of reference points whose positions are obtained as coordinate points on a single reference coordinate system by the reference coordinate calculation method.
According to this configuration, since the reference coordinate calculation method is not limited to the area where the reference points are arranged, the surface plate can have a reference point in as wide an area as necessary. As a result, for example, a surface plate suitable for measuring a large workpiece such as a car or an airplane can be obtained. And since the said reference coordinate calculation method is a low-cost method which does not require a separate large-sized measuring machine, a large surface plate can be manufactured at low cost.
Here, the surface plate includes not only the surface plate in which the reference point is arranged on the table, but also one in which the reference point is arranged on the floor surface, for example.

The shape measuring apparatus of the present invention includes the surface plate and a measuring machine movable on the surface plate.
In such a configuration, a workpiece is placed on a surface plate having a reference point in a wide area, and the workpiece is measured with a measuring machine while recognizing the position based on each reference point. Then, a workpiece larger than the measurement area of the measuring machine can be measured.
And, when calculating and registering the position of the reference point arranged on the surface plate as a point on the reference coordinate system, a measuring machine for measuring the workpiece can be used, so that the cost is greatly reduced. be able to.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be illustrated and described with reference to reference numerals attached to respective elements in the drawings.
(First embodiment)
A first embodiment according to the shape measuring apparatus of the present invention will be described.
First, the configuration of the shape measuring apparatus will be described.
FIG. 1 is a diagram showing the overall configuration of the shape measuring apparatus, FIG. 2 is a diagram showing the structure of a reference point of the surface plate, and FIG. 3 is a diagram showing the configuration of an arithmetic processing unit.
The shape measuring apparatus 100 includes a surface plate 200, a measuring machine 300, an arithmetic processing unit 400, an input unit 500, and an output unit 600.

The surface plate 200 is a large surface plate having a side exceeding 2 m, for example, and the workpiece (object to be measured) W and the measuring machine 300 are placed on the surface plate 200.
The surface plate 200 is provided with a plurality of reference points R.
For example, the reference points R are arranged in a grid pattern on the surface plate 200, and 6 × 6 pieces are provided at a pitch of 400 mm. Specifically, a conical hole 210 into which a reference ball 220 processed into a true sphere can be fitted is formed on the surface plate 200 (see FIG. 2), and the position of each reference point R is a hole. Let it be the center point of the reference ball 220 fitted in 210.
In this embodiment, the coordinate value obtained by projecting the center point of the reference ball 220 perpendicularly to the surface of the surface plate is set as the reference point coordinate Cr, and the reference point coordinate Cr for each reference point R is set on a single reference coordinate system. While calculating | requiring and memorize | storing as a coordinate point, a big workpiece | work is measured using this reference | standard point coordinate.
Here, in obtaining the center point of the reference ball 220, an arbitrary four points on the surface of the reference ball 220 are measured, and the center coordinate value of the reference ball 220 is calculated based on these four points. . Then, by projecting the center point of the reference ball 220 onto the surface of the surface specified by measuring three points (for example, B _{1 to} B _{3 in} FIG. 1) that are not positioned on a straight line on the surface plate 200. A reference point coordinate Cr for the reference point R is obtained.
A method of obtaining the reference point coordinates for each reference point as a point on the unified reference coordinate system will be described later with reference to FIGS.

The measuring machine 300 is a measuring machine that can be carried or moved by being provided with a moving leg ring (caster), for example, a multi-indirect type three-dimensional measuring machine. The measuring machine 300 is placed on the surface plate 200 and its position is moved according to the measurement site of the workpiece W.
The measuring instrument 300 includes a pedestal part 310, a movable arm part 320 connected to the pedestal part 310 so that the posture can be changed via a joint 324, a touch probe 330 rotatably connected to the tip of the movable arm part 320, Is provided.
The movable arm portion 320 is configured by connecting a first arm 321, a second arm 322, and a third arm 323 with universal joints 325 and 326 so that their angles can be changed. A touch probe 330 that contacts the workpiece W and detects the workpiece surface is connected to the tip of the third arm 323 via a universal joint 327.

  As shown in FIG. 3, the arithmetic processing unit 400 includes a reference point coordinate calculation unit 410, a reference point coordinate storage unit 420, a position and orientation recognition unit 430, a coordinate system conversion unit 440, and a measurement data storage unit 450. And a workpiece shape analysis unit 460.

The configuration of the reference point coordinate calculation unit 410 and the reference point coordinate calculation method (operation of the reference point coordinate calculation unit) will be described with reference to FIGS.
FIG. 4 is a diagram illustrating the configuration of the reference point coordinate calculation unit 410. FIG. 5 is a flowchart showing a procedure for calculating the reference point coordinates, FIG. 6 is a diagram showing an example of grouping when the position of the reference point is measured, and FIG. 7 is a reference point coordinate conversion function for each group. It is a flowchart which shows the procedure which calculates.
Hereinafter, the processing operation in which the procedure shown in FIGS. 5 and 7 is executed by the configuration shown in FIG. 4 will be described.

In ST100 in FIG. 5, a reference position number j (j = 1, 2, 3,...) Is assigned (numbered) to each reference point R.
For example, as shown in FIG. 1, each reference point is numbered sequentially from R ₁ . Thus, the reference position number j assigned to each reference point R is stored in the reference point number storage unit 411.

In ST101, the reference points R on the surface plate 200 are grouped for each range (measurement region) that can be measured by the measuring device 300 without moving the measuring device 300 (grouping step). At this time, grouping is performed so that each group includes two or more common reference points R with at least one other group. For example, in FIG. 6, the reference point R3 and the reference point R7 are common between G1 and G2.
Such a grouping process is executed by a program preset in the grouping means 412, and a program that is automatically executed when the array of the reference points R and the measurement region of the measuring device 300 are input. It is incorporated in the grouping means 412.

In ST102, coordinates obtained by projecting the position of each reference point R on the surface plate are obtained as measurement values for each group.
That is, first, the center point of the reference ball 220 is calculated in a state where the reference ball 220 is fitted in the hole 210, and then the center of the reference ball 220 is placed on the surface plate surface identified from the three points on the surface plate 200. A coordinate point on which the point is projected is obtained as a measurement value.
For example, in FIG. 6, in obtaining the coordinates of the reference points (R ₁ , R ₂ , R ₃ , R ₅ , R ₆ , R ₇ ) in the group G 1, (1) the group from the three points on the surface of the surface plate 200. Determine the surface plate surface (common plane) when measuring the reference points (R _{1 to} R ₃ , R _{5 to} R ₇ ) of G1, and (2) the reference fitted in the reference point R (for example, the reference point R ₁ ) The center point of the reference ball 220 is obtained from the four points on the surface of the ball 220, and (3) the center point of the reference ball 220 is projected on the surface of the surface plate, and the reference point coordinate Cr of the reference point R in G1 is obtained as a measured value.
Similarly, in other groups and other reference points R, coordinate points (reference point coordinates Cr) obtained by projecting the reference points R onto the surface plate are obtained as measurement values.

Here, in obtaining the common plane (surface plate surface) in each group, for example, three points that are not positioned on a straight line on the surface plate, such as B _{1 to} B _{3 in} FIG. 1, are measured. Identify the plane from the value.
In obtaining the center point of the reference ball 220, four points on the surface of the reference ball 220 may be measured, and the center of the reference ball 220 may be obtained from the measured values of these four points. When the diameter (or radius) is known, three points on the surface of the reference ball 220 may be measured, and the center point of the reference ball 220 may be obtained from the measurement value and the diameter of these three points.

In the case of grouping as shown in FIG. 6, since the reference points common to the groups are included, the reference points R ₁ , R ₂ , R ₄ , R ₉ , R ₁₀ , R ₁₂ are measured only once. On the other hand, the measurement of the reference points R ₃ , R ₅ , R ₆ , R ₈ , R ₁₁ is performed twice, and the measurement of the reference point R ₇ is performed four times.
At this time, since the origin of measurement differs depending on the position of the measuring device 300 itself, even when the reference point coordinate Cr of the reference point R common between adjacent groups is measured, the reference point coordinate Cr ( The x-coordinate and y-coordinate) are (20, 20) on the one hand and (30.01, 10) on the other hand.
The measurement values obtained by such measurement are sequentially stored in the measurement value storage unit 413, and the measurement values are stored in association with the reference point number j stored in the reference point number storage unit 411.

In ST103, a reference point coordinate conversion function F for converting a measurement value obtained by measuring the reference point R into a coordinate point on the reference coordinate system is calculated for each group.
This process will be described with reference to the flowchart of FIG.

The measurement value (reference point coordinate Cr) of each reference point R obtained by the measurement is stored in the measurement value storage unit 411 in association with the reference point number j. In ST200 of FIG. A measurement number i is given to the measured value obtained by the measurement. That is, the measurement number i is assigned to the measurement value obtained redundantly for the reference point R included in common among the groups. Here, the measurement number i is i = 1, 2,..., N _j , and n _j represents the number of data obtained redundantly for the reference point R _j . Then, an identification number P _ji is _assigned to the measurement value P having the reference position number j and the measurement number i. Here, P represents a two-dimensional vector composed of an x-coordinate value and a y-coordinate value.
In ST201, the group number to which the measurement value P _ji belongs is _assigned to the measurement value P _ji .
The group number assignment is performed by the group number assignment unit 414 in response to the data output from the measurement value storage unit 413.
The group number assigning unit 414 associates a group (G1, G2,...) To which the measurement value P _ji belongs to the reference point number j and the measurement number i according to the grouping by the grouping unit 412. Generate automatically. The group number assigning unit 414 assigns a group number g (ji) to the measurement value P _ji with reference to this table. Here, g (ji) is a function representing the group number (that is, G1, G2,...) To which the measured value _Pji having the reference point number j and the measurement number i is belonging.
That is, the grouping means 412 groups the reference points R while having a common reference point between the groups as in the groups G1, G2,... The group number g (ji) for indicating in which group the measurement value P _ji whose measurement number is the i-th measurement value is obtained.

Next, in ST202, a reference point coordinate conversion function for converting the measured value P _ji into the reference coordinate system is temporarily set as F _{g (ji)} .
Here, the reference point coordinate conversion function F is a matrix representing a mapping for transferring measured values from the coordinate system when the reference point R is measured by the measuring instrument 300 to the reference coordinate system. For example, it is expressed in the following form (Formula 1), and is set and input to the reference point coordinate conversion function temporary setting unit 415 and stored.
In the case of (Expression 1), the parallel movement corresponds to the origin movement accompanying the movement of the measuring instrument 300, and the rotation operation corresponds to the inclination (relative posture) between the measuring instrument 300 and the surface plate.

In ST203, a reference point coordinate conversion function F _{g (ji)} is calculated.
This reference point measured data _{P ji} of the _{R j} obtained was measured in duplicate at different groups (where, i = 1, 2, ~n _j, where, _{n j} is duplicated for the reference points _{R j} Temporarily set in the reference point coordinate conversion function temporary setting unit 415 so that the value “F _{g (ji)} (P _ji )” obtained by coordinate conversion for the obtained data number) is the same value (or a very approximate value). This is done by adjusting the reference point coordinate conversion function F _{g (ji)} . That is, the reference point coordinate conversion function F _{g (ji)} is obtained by minimizing the sum of the squares of the deviations by the least square method as follows.

  In such processing (ST203), in the reference point coordinate conversion function calculation means 416, the measurement value stored in the measurement value storage unit 413 is temporarily set in the reference point coordinate conversion function temporary setting unit 415 (Formula 1). This is performed by assigning and applying (Equation 2) and (Equation 3).

In ST104 of FIG. 5, the process of converting the measurement value _Pji into the reference coordinate system for each group (G1, G2,...) By the coordinate conversion function Fg _(ji) calculated in ST103 is a reference point coordinate conversion process. Performed by means 417.
In ST105, the reference point coordinate Cr of each reference point R calculated by the conversion process in ST104 is registered in the reference point coordinate storage unit 420. However, when there are a plurality of converted values for the same reference point R, the average value thereof is used.

Next, the configuration of the arithmetic processing unit 400 will be described, and the case where the workpiece is measured using the reference point coordinates in the reference coordinate system stored in the reference point coordinate storage unit 420 will be described.
The reference point coordinate storage unit 420 includes a reference point coordinate Cr for each reference point R calculated by the reference point coordinate calculation unit 410 and a number j (j = 1, 2,...) Assigned to each reference point R. I remember it in pairs.
The position / orientation recognition unit 430 recognizes the position of the measuring device 300 on the surface plate 200 and the posture of the measuring device 300 (such as an inclination angle with respect to the surface plate 200). The position and orientation recognition unit 430, a point on the surface plate surface 200 (e.g., FIG. 1 in _B 1 .about.B _3, provided that _B 1 .about.B ₃ points not on a straight line) in the result of measurement with measuring machine 300 A surface plate surface calculation unit 431 that calculates a relative attitude between the surface plate surface and the measuring machine 300 based on the connection is connected.
The position / orientation recognition unit 430 recognizes the position and orientation of the measuring machine 300 based on the surface plate surface calculated by the surface plate surface calculation unit 431 and the coordinate values obtained by measuring the two reference points R. .

The coordinate system conversion unit 440 converts the measurement value obtained by measuring the workpiece W by the measuring machine 300 placed on the surface plate 200 into a coordinate point on the reference coordinate system.
In addition, a measurement point coordinate conversion function calculation unit 441 is connected to the coordinate system conversion unit 440, and the measurement point coordinate conversion function calculation unit 441 detects the position and orientation of the measuring machine 300 recognized by the position and orientation recognition unit 430. Based on the above, a measurement point coordinate conversion function for converting a measurement value obtained by the measuring instrument 300 into a reference coordinate system is calculated.

The measurement data storage unit 450 stores, as measurement data, a value obtained by converting a measurement value obtained by measuring the workpiece W into a coordinate point on the reference coordinate system by the coordinate system conversion unit 440.
The workpiece shape analysis unit 460 analyzes the workpiece shape based on the measurement data stored in the measurement data storage unit 450. For example, a comparative evaluation with respect to a master work or a design value can be given as an example.

Next, the workpiece measuring operation by the shape measuring apparatus 100 will be described.
First, a coordinate value on the reference coordinate system is obtained for the reference point coordinate Cr of each reference point R provided on the surface plate 200 and registered in the reference point coordinate storage unit 420. This process is as described with reference to FIGS.
The workpiece W to be measured is placed on the surface plate 200, and the measuring machine 300 is placed at a position corresponding to the measurement site of the workpiece W.

Before the workpiece W is actually measured, any three points on the surface plate 200 (for example, B _{1 to} B ₃ , but B _{1 to} B ₃ are used by the measuring device 300 to recognize the position and orientation of the measuring device 300. Are not on a straight line) and two reference points R are measured. The measurement of the reference point R means that the center point of the reference ball 220 is obtained by measuring four points on the surface of the reference ball 220 with the reference ball 220 fitted in the hole 210. This refers to obtaining a point (reference point coordinate) obtained by projecting a point on a surface plate.
Based on the result of measuring three points on the surface plate 200, the surface plate surface calculation unit 431 determines the relative posture between the surface plate surface and the measuring machine 300. The values (reference point coordinates) obtained by measuring the two reference points R are compared with the reference point coordinates on the reference coordinate system stored (registered) in the reference point coordinate storage unit 420, and the position and orientation recognition unit At 430, the position and orientation of the measuring device 300 are obtained.
A measurement point coordinate conversion function calculation unit 441 generates a measurement point coordinate conversion function for converting a measurement value obtained by the measurement device 300 into a reference coordinate system according to the position and orientation of the measurement device 300 recognized by the position / orientation recognition unit 430. Calculated. The calculated measurement point coordinate conversion function is output to the coordinate system conversion unit 440.

Next, the workpiece W is actually measured by the measuring machine 300.
At this time, the measurement is performed for each region that can be measured at the current position of the measuring device 300 without changing the position of the measuring device 300.
The measurement value obtained by measuring the workpiece W is output to the coordinate system conversion unit 440, and the coordinate system conversion unit 440 converts the measurement value into a point on the reference coordinate system using the measurement point coordinate conversion function.
A value converted into a point on the reference coordinate system is stored in the measurement data storage unit 450.

When the position of the measuring instrument 300 is changed, the three points on the surface plate 200 and the two reference points R are measured again to recognize the position and orientation of the measuring instrument 300.
Based on the measurement data stored in the measurement data storage unit 450, the workpiece shape analysis unit 460 performs shape analysis of the workpiece W. For example, a comparison with a master work or a design value is given as an example.

According to the shape measuring apparatus 100 having such a configuration, the following effects can be obtained.
(1) By measuring each reference point R by grouping and obtaining a measurement value coordinate conversion function F for each group, the position of the reference point R in a wide range can be determined using the measuring device 300 having a narrow measurement area as a reference coordinate. It can be calculated and registered as a coordinate point on the system. At this time, since the coordinates of the reference point R can be obtained using the measuring device 300 used for measuring the workpiece W, the cost can be significantly reduced as compared to separately preparing a large measuring device. .

(2) When obtaining the coordinates of each reference point R (reference point coordinates) as points on a single reference coordinate system, grouping and measuring each reference point R, the coordinate conversion function F for each group is calculated. Therefore, the width of the range in which the reference point R is provided is not limited and can be as wide as necessary. For example, there is a limit in the measurable area even with a laser length measuring device or the like, but according to the present embodiment, it is possible to measure even a large workpiece (for example, a car or an airplane).

(3) In the present embodiment, the coordinate point where the position of the reference point is projected on the surface plate is used as the reference point coordinate, and the reference point coordinate arranged on the common plane is obtained. As a result, even when a common reference point is measured among the groups and the results measured for each group based on the coordinates of these common reference points are combined as points on a unified coordinate system, they are common among the groups. Two or more reference points can be provided. In general, in an n-dimensional coordinate system, n common reference points are required between groups, and by measuring two common reference points between groups and measuring a common plane in each group, This is because the same effect can be obtained as if the three reference points were included in common among the groups. In this way, since two reference points can be shared between groups, the grouping conditions are relaxed compared to the case where three groups are shared, and grouping can be performed easily.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
The reference points on the surface plate are not limited to being arranged in a grid pattern, and may be randomly arranged.
As a method of grouping reference points, grouping may be performed so that three reference points are shared with other groups. In this case, it is not necessary to project the center of the reference ball onto the surface plate, and the center of the reference ball 220 is used as it is as the reference point coordinates. Then, the process of calculating the surface plate surface by measuring three arbitrary points on the surface plate surface can be omitted. Note that when the reference point is a point on a two-dimensional coordinate system, such as a reference point used in an image measuring machine, two reference points may be common between groups.

  Here, when grouping the reference points, as shown in FIG. 6, it is preferable that the group forms a closed loop as a whole. For example, if there are a start point group and an end point group in the grouped group, the coordinate transformation function is calculated based on a common reference point between the groups. There is a possibility that the standard coordinate system may not be unified with other groups, but all groups are connected (linked) to form a standard coordinate system that eliminates error accumulation. it can.

In addition, when the position of the reference point R is used as the reference point coordinates without projecting onto the common plane, the step of specifying the surface plate is omitted in recognizing the position and orientation of the measuring machine, and only three The position of the measuring machine may be recognized by measuring the reference point.
The configuration of the measuring device is not particularly limited, and for example, a laser length measuring device may be used. Then, it is possible to further expand the measurement area of the laser length measuring instrument that originally has a wide measurement area. In this case, the interval between the reference points may be increased according to the measurement region of the laser length measuring device. When the reference point is a point on the two-dimensional coordinate system, the measuring machine is a two-dimensional sensor like an image measuring machine.

  The present invention can be used for a shape measuring apparatus. In particular, it can be used for a shape measuring apparatus that measures a large workpiece.

The figure which shows the whole structure of a shape measuring apparatus in 1st Embodiment which concerns on the shape measuring apparatus of this invention. The figure which shows the structure of the reference point of a surface plate in the said 1st Embodiment. The figure which shows the structure of the arithmetic processing part in the said 1st Embodiment. The figure which shows the structure of the reference point coordinate calculation part in the said 1st Embodiment. The flowchart which shows the procedure which calculates a reference point coordinate in the said 1st Embodiment. The figure which shows an example of grouping in the case of measuring the position of a reference point in the said 1st Embodiment. The flowchart which shows the procedure which calculates the coordinate transformation function for every group.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Shape measuring apparatus, 200 ... Surface plate, 210 ... Hole, 220 ... Reference | standard ball | bowl, 300 ... Measuring machine, 310 ... Base part, 320 ... Movable arm part, 321 ... 1st arm, 322 ... 2nd arm, 323 ... 3rd arm, 324 ... joint, 325, 326, 327 ... universal joint, 330 ... touch probe, 400 ... arithmetic processing unit, 410 ... reference point coordinate calculation unit, 411 ... reference point number storage unit, 412 ... grouping means, 413 Measured value storage unit 414 Group number assigning unit 415 Reference point coordinate conversion function temporary setting unit 416 Reference point coordinate conversion function calculation unit 417 Reference point coordinate conversion processing unit 420 Reference point coordinate storage unit 430 ... Position and orientation recognition unit, 431 ... Surface plate surface calculation unit, 440 ... Coordinate system conversion unit, 441 ... Measurement point coordinate conversion function calculation unit, 450 ... Measurement data storage unit, 460 Workpiece shape analysis unit, 500 ... input unit, 600 ... output means.

Claims (9)

A reference coordinate calculation method for obtaining positions of a plurality of reference points arranged on a surface plate wider than a measurement area of a measuring machine as coordinate points on a single reference coordinate system,
The reference points included in a region that can be measured without moving the position of the measuring machine itself as one group, and each group obtained by grouping a plurality of the reference points is at least one other group. A grouping step that includes the three reference points in common, and that all groups form a closed loop having no start point group and no end point group as a whole, and are grouped so as to be connected in series;
A measuring step of measuring the position of the reference point for each group with the measuring instrument;
Reference point coordinates for calculating for each group a reference point coordinate conversion function for converting the respective positions obtained by measuring in different groups with respect to the reference point common to different groups to the same or very similar coordinate points A conversion function calculation step;
A reference point coordinate conversion processing step of performing coordinate conversion of the position of each reference point measured for each group by the reference point coordinate conversion function calculated for each group. A reference coordinate calculation method for obtaining positions of a plurality of reference points arranged on a surface plate wider than a measurement area of a measuring machine as coordinate points on a single reference coordinate system,
The reference points included in a region that can be measured without moving the position of the measuring machine itself as one group, and each group obtained by grouping a plurality of the reference points is at least one other group. A grouping step that includes two reference points and a common plane in common, and that all groups form a closed loop having no start point group and no end point group as a whole, and are grouped so as to be connected in series.
A measuring step of measuring the position of the reference point and the common plane for each group with the measuring device;
A reference point coordinate conversion function is calculated for each group that converts the positions obtained by measuring the reference point and the common plane common to different groups in different groups to the same or very similar coordinate points. A reference point coordinate conversion function calculation step to perform,
A reference point coordinate conversion processing step of performing coordinate conversion of the position of each reference point measured for each group by the reference point coordinate conversion function calculated for each group. In the reference coordinate calculation method according to claim 2,
The reference coordinate calculation method, wherein the position of the reference point is a position projected on the common plane. A reference coordinate calculation method for obtaining positions of a plurality of reference points, which are points on a two-dimensional coordinate system arranged on a surface plate wider than a measurement area of a measuring machine, as coordinate points on a single reference coordinate system,
The reference point included in an area that can be measured without moving the position of the measuring machine itself is regarded as one group, and each group obtained by grouping a plurality of the reference points is at least 2 between at least one other group. A grouping step that includes two reference points in common, and that all groups form a closed loop that does not have a start point group and an end point group as a whole, and are grouped so as to be connected in series.
A measuring step of measuring the position of the reference point for each group with the measuring instrument;
Reference point coordinates for calculating, for each group, a reference point coordinate conversion function for converting the respective positions obtained by measuring the reference points common to different groups into different groups to the same or very similar coordinate points. A conversion function calculation step;
A reference point coordinate conversion processing step of performing coordinate conversion of the position of each reference point measured for each group by the reference point coordinate conversion function calculated for each group. In the reference coordinate calculation method according to any one of claims 1 to 4,
The reference point coordinate conversion function calculation step includes:
The coordinates obtained by measuring the position obtained by measuring the same reference point in different groups with the coordinate conversion function are obtained with respect to the average value of each coordinate point, and the sum of squares of the deviation is minimized. The reference point coordinate conversion function is calculated. A reference coordinate calculation method characterized by:   6. A reference coordinate calculation program that causes a computer to execute each step of the reference coordinate calculation method according to claim 1.   The recording medium which recorded the reference coordinate calculation program of Claim 6 so that computer reading was possible.   6. A surface plate comprising a plurality of reference points whose positions are obtained as coordinate points on a single reference coordinate system by the reference coordinate calculation method according to claim 1. A surface plate according to claim 8,
A shape measuring apparatus comprising: a measuring machine movable on the surface plate.

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